Regulation of λ exonuclease: I. Properties of λ exonuclease purified from lysogens of λ T11 and wild type

Abstract

Lambda exonuclease was purified 133 times from the hyperactive mutant lysogen, W3350(λT11) and 1000 times from the wild-type lysogen, W3350(λ+). The following properties of the two enzymes were similar: (1) strong specificity for native DNA; (2) pH optimum; (3) divalent cation requirement; (4) Km; and (5) inhibition by sodium chloride. Inhibition and competition experiments with antiserum prepared against partially purified λT11 exonuclease demonstrated immunologic similarity and similar enzymic activity per mole of enzyme. These data indicate that the active site of λT11 exonuclease has not been mutationally altered. In the last stage of purification from λT11 by chromatography on phosphocellulose, exonuclease activity was repeatedly eluted in two sharp peaks. The activity in both peaks was identical by the enzymic and immunologic criteria listed above. Both peaks contained exonuclease activity which filtered through Sephadex G100 with a mobility similar to that of bovine serum albumin (mol. wt 67,000).